#include <asm/thread_info.h>
#include <asm/processor-flags.h>
-/*G:020 This is where we begin: head.S notes that the boot header's platform
- * type field is "1" (lguest), so calls us here. The boot header is in %esi.
+/*G:020 Our story starts with the kernel booting into startup_32 in
+ * arch/x86/kernel/head_32.S. It expects a boot header, which is created by
+ * the bootloader (the Launcher in our case).
+ *
+ * The startup_32 function does very little: it clears the uninitialized global
+ * C variables which we expect to be zero (ie. BSS) and then copies the boot
+ * header and kernel command line somewhere safe. Finally it checks the
+ * 'hardware_subarch' field. This was introduced in 2.6.24 for lguest and Xen:
+ * if it's set to '1' (lguest's assigned number), then it calls us here.
*
* WARNING: be very careful here! We're running at addresses equal to physical
* addesses (around 0), not above PAGE_OFFSET as most code expectes
* (eg. 0xC0000000). Jumps are relative, so they're OK, but we can't touch any
- * data.
+ * data without remembering to subtract __PAGE_OFFSET!
*
* The .section line puts this code in .init.text so it will be discarded after
* boot. */
.section .init.text, "ax", @progbits
ENTRY(lguest_entry)
- /* Make initial hypercall now, so we can set up the pagetables. */
+ /* We make the "initialization" hypercall now to tell the Host about
+ * us, and also find out where it put our page tables. */
movl $LHCALL_LGUEST_INIT, %eax
movl $lguest_data - __PAGE_OFFSET, %edx
int $LGUEST_TRAP_ENTRY
/* The Host put the toplevel pagetable in lguest_data.pgdir. The movsl
- * instruction uses %esi implicitly. */
+ * instruction uses %esi implicitly as the source for the copy we're
+ * about to do. */
movl lguest_data - __PAGE_OFFSET + LGUEST_DATA_pgdir, %esi
/* Copy first 32 entries of page directory to __PAGE_OFFSET entries.